1. Field of the Invention
Well known, in the art of tire making, is the formation, during one part of the tire production process, of an uncured tire. Typically, the uncured tire will include a plurality of biases, or reinforcing portions.
2. Description of the Prior Art
To date, one widely used method of bias tire production known to applicants employs a drum, upon which the various biases and/or belts and constituents comprising the uncured green tire product (or "tire preform") to be produced are assembled. Well known in the art is the process whereby, dependent upon expected working loads, an initial tire preform is fabricated on the drum, and then the resulting preform is formed into the final product, for example, through the use of an internal bladder and an external mold, in which the tire preform is simultaneously formed and cured under heat and pressure.
It will be appreciated that the form (or "drum") upon which the tire preform is constructed must exhibit, throughout the formation process and over its useful lifetime, a given degree of "circularity" or "roundness" or, in other words, a conformance to specifications. Prior tire forming drums are known to applicants which include a series of circumferential segments fabricated of metal and located peripherally about a central hub. The peripheral circumferential surfaces and the segments of such known prior art devices are interconnected with the central hub through linkage mechanisms which may be actuated to either expand or contract the circumferential segments. Thus, the prior art tire forming drums known to applicants involve a diameter altering mechanism which mechanically collapses the drum into itself. These drums are dependent upon the accuracy and specifications to which the linking mechanism is manufactured and to the wear to which such mechanism and the drum itself are subject to during use. Lack of precision relating to the lack of roundness, concentricity, etc. of the drum degrades the quality of the tires produced, increases their rejection rate during manufacture and their failure rate during use. Accordingly, using these prior art arrangements, production and warranty costs are increased.